1. Field of the Invention
The present invention relates to a rotor blade for a power-plant fitted with a device optimizing aerodynamics.
2. Description of Related Art
Wind-driven power-plants comprise a rotor fitted with one or more rotor blades. Each rotor blade in turn comprises a sectional blade contour, which is perpendicular to the blade's direction from blade root to blade tip, and of which the thickness decreases toward the outside, from the blade root toward the blade tip. The blade contour entails a suction side and a pressure side, so that when air is moving around the blade, the suction side is at a lower pressure than the pressure side. The pressure differential across the pressure and suction sides generates lift causing the rotor rotation, which in turn is used to drive an electric power generator.
High rotor efficiency and hence high wind-driven power-plant output assumes, as smooth as possible, an airflow around the blade contour perpendicularly to the axis of the rotor blade and over the entire range of the rotor blades.
However, it is noted with respect to known rotor blades that the airflow moving around the blade contour will detach at the suction side and that a wake zone is generated which, by increasing drag, reduces the rotor blade lift and decelerates the rotor blade. Typically, the term “wake zone” denotes the region of the detached airflow. Both factors lower the wind-driven power-plant productivity.
Seen in the direction of flow, airflow detachment as a rule takes place beyond the highest relative depth of the blade contour. In general, at least the zones near the blade root will be affected.
Vortex generators are a known means to reduce airflow detachment and thus to optimize aerodynamic airflow around the blade contour. Such generators, as a rule, are in the form of sheetmetal, bars or cross-sectionally shaped structures and the like configured at the suction side of the rotor blade and generating local turbulences reducing large-area detachment of the airflow around the blade contour. Illustratively, such vortex generators are known form the patent document WO 0015961. These known vortex generators incur the drawback that they only slightly improve wind-driven power-plant productivity because they themselves generate drag and furthermore are very noisy.